Force sensing device

Abstract

A force or pressure sensing device comprises one or more magnets resiliently held spaced from one or more magnetic sensors such that pressure on the device displaces the magnets relative to the magnetic field sensors. The device may be incorporated into an insole of a shoe, or integrated into a shoe, or integrated into a seat, cushion, mattress or saddle. The device includes one or more magnetic focussing elements on the opposite side of the magnetic field sensor from the magnets to focus and condition the magnetic field passing through the sensor. The magnetic focussing elements may be permanent magnets or magnetic materials having a high magnetic permeability such as mu-metals. Additional magnetic focussing elements may be placed adjacent to the magnets. Plural magnetic field sensors can be arranged in a symmetrical arrangement in a plane below the one or more magnets so that shear forces applied to the device causes lateral relative displacement of the magnet and magnetic field sensors changing the magnetic field sensed by the magnetic field sensors. The device can also include a motion detector such as an accelerometer which may be integral with the magnetic field sensor.

1 . A force sensing device comprising a magnetic field generator, a magnetic field sensor, a resilient support supporting the magnetic field generator and magnetic field sensor for relative movement in response to force applied to the device, the magnetic field sensor being disposed to measure changes in the magnetic field from the magnetic field generator resulting from such relative movement, the magnetic field sensor being a magnetoresistance sensor operative to sense relative movements of the magnetic field generator and magnetic field sensor in two orthogonal directions whereby the force sensing device senses both compressive and shear force applied to the force sensing device. 
     
     
         2 . A force sensing device according to  claim 1  wherein the magnetoresistance sensor is operative to sense relative movements of the magnetic field generator and magnetic field sensor in three orthogonal directions. 
     
     
         3 . A device according to  claim 1 , wherein the resilient support comprises a first layer which is resilient and supports the magnetic field generator and a second resilient layer between the magnetic field generator and the magnetic field sensor. 
     
     
         4 . A device according to  claim 3  further comprising a third layer on the opposite side of the second layer from the first layer.